This invention relates to novel compounds which are inhibitors of protein tyrosine kinases such as the Janus kinases, also referred to as JAK1, JAK2, JAK3 and TYK2. Said compounds are useful in the treatment of diseases related to activity of Janus kinases, including, for example, psoriasis, atopic dermatitis, rosacea, lupus, multiple sclerosis, rheumatoid arthritis, Type I diabetes and complications from diabetes, asthma, cancer, autoimmune thyroid disorders, ulcerative colitis, Crohn's disease, Alzheimer's disease, leukaemia, eye diseases such as diabetic retinopathy and macular degeneration as well as other autoimmune diseases and indications where immunosuppression would be desirable for example in organ transplantation.
Protein tyrosine kinases are a family of enzymes catalysing the transfer of the terminal phosphate of adenosine triphosphate to tyrosine residues in protein substrates. Phosphorylation of tyrosine residues on protein substrates leads to transduction of intracellular signals which regulate a wide variety of intracellular processes such as growth, differentiation and activation of cells of the immune system. As activation of T-cells and B-cells as well as other cells of the immune system such as monocytes and macrophages is implicated in a number of inflammatory conditions and other disorders of the immune system (e.g. autoimmune diseases), modulation of the activity of protein tyrosine kinases appears to be an attractive route to the management of inflammatory diseases. A large number of protein tyrosine kinases have been identified which may be receptor protein tyrosine kinases, e.g. the insulin receptor, or non-receptor protein tyrosine kinases.
The protein tyrosine kinases JAK1, JAK2, JAK3 and TYK2 have essential roles in cytokine-dependent regulation of proliferation and function of cells involved in immune response. They are critical in signal transduction in response to their activation via tyrosine phosphorylation by stimulation of interleukin receptors. (1) Schindler C. et al. JAK-STAT signaling: from interferons to cytokines. J. Biol. Chem. 2007; 282(28):20059; 2) O'Shea J. J. Targeting the Jak/STAT pathway for immunosuppression Ann. Rheum. Dis. 2004; 63 Suppl 2:ii67; 3) Schindler C. Series introduction. JAK-STAT signaling in human disease. J. Clin. Invest. 2002; 109(9):1133).
While JAK1, JAK2 and TYK2 are ubiquitously expressed JAK3 is predominantly expressed in hematopoietic cells.
JAK1 plays a critical role in mediation of biological responses and JAK1 is widely expressed and associated with several major cytokine receptor families. It is involved in signalling by members of the IL-2 receptor family (IL-2, IL-4, IL-7R, IL-9R, IL-15R and IL-21R), the IL-4 receptor family (IL-4R, IL-13R), the gp130 receptor family and class II cytokine receptors.
JAK2 is implicated in signalling by several single chain receptors (including Epo-R, GHR, PRL-R), the IL-3 receptor family, the gp130 receptor family and Class II receptor cytokine family. Thus, JAK2 plays a critical role in transducing signals for Epo, IL-3, GM-CSF, IL-5 and IFNγ. JAK2 knockout mice exhibit an embryonic lethal phenotype.
JAK3 is involved in signal transduction by receptors that employ the common gamma chain of the type I cytokine receptor family (e.g. IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21). XSCID patient populations have been identified with reduced levels of JAK3 protein or with genetic defects to the common gamma chain, suggesting that immune suppression should result from blocking signalling through the JAK3 pathway. Animal studies have suggested that JAK3 not only plays a critical role in B and T lymphocyte maturation, but that JAK3 is constitutively required to maintain T cell function. Modulation of immune activity through this novel mechanism can prove useful in the treatment of T cell proliferative disorders such as immune system diseases, in particular autoimmune diseases.
TYK2 is implicated in type I interferons, IL-6, IL-10, IL-12 and IL-23 signalling. A human patient with a TYK2 deficiency has been described and this patient had a primary immunodeficiency disorder characterized as a hyper-IgE-like syndrome with many opportunistic infections by virus, bacteria and fungi. Because Il-23 has been found to play an important role in many chronic inflammatory conditions, a TYK2 inhibitor could conceivably be very effective in treating diseased influenced by IL-23.
Inhibitors of the Janus kinases are accordingly expected to show utility in the treatment of inflammatory and non-infectious autoimmune diseases wherein these kinases are involved.
It is further envisaged that compounds of the present invention may be useful as inhibitors of other kinases, such as Src family kinases (Src, Yes, Fyn, Lyn, Fgr, Blk, Lck and/or Hck) responsible for receptor mediated signalling in T, B and other immune cells; Raf-1/Ras, MAP kinase signalling pathway; Syk and ZAP70 kinases responsible of activation of immune cells.
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